ABSTRACT
The classical view of human-machine systems depicts a human and a machine that are linked by inputs and outputs (see Figure 1). The control input to the machine determines whether the machine changes state or remains in the same state. As a result of this, some output is produced — for instance a set of measurements that indicate the state of the machine and the value of specific process parameters. The measurements, or the output from the machine, become the input to the human operator. According to the classical view, this input is “processed’’ by the operator and results in a response or output that becomes the control input to the machine. While the engineering sciences, such as control theory, have focused on describing how the machine works, the behavioral sciences have been more concerned with describing how the operator works, i.e. what goes on between receiving the input and producing the output.
